Consciousness and Sleep & Coma

Page 1: Introduction

  • Title: Physiology of Consciousness and Sleep

  • Author: Dr. Mar Mar Lwin

  • Date: 23.10.2024

Page 3: Definitions

Consciousness

  • A state of being interactive with the surrounding environment.

  • Mediated by the arousal system (Reticular Activating System, RAS).

Coma

  • State of prolonged unconsciousness with loss of reaction to external stimuli.

  • Characteristics of coma include:

    • Stupor: Unconscious but can be aroused with repeated stimuli.

    • Delirium: Confused state, can include restlessness and hallucinations.

    • Locked-in syndrome: Conscious but unable to speak or move due to brainstem damage.

    • Vegetative state: Appearing awake but unresponsive (widespread cortical damage).

Page 4: Reticular Activating System (RAS)

  • Network of neurons in the brainstem projecting to the hypothalamus, thalamus, and cortex.

  • Responsible for:

    • sensation, consciousness, attention, and maintaining the sleep-wake cycle.

  • Transmits sensory messages to the cerebral cortex via the thalamus, alerting the brain to incoming stimuli.

  • Involves regulation of voluntary movements, autonomic functions, and muscle tone through spinal cord connections via descending RAS.

Page 5: Ascending Connections

  • Consciousness regulated by RAS and ascending connections to the thalamus and cortex.

  • Located in midbrain.

Page 6: Arousal System

  • Ascending arousal system in the brainstem, affecting the intralaminar nuclei of the thalamus and cortical areas.

Page 7: RAS Connections

  • Receives inputs from:

    • Cortex and all sensory pathways.

    • Cerebellum, thalamus, hypothalamus, and basal ganglia.

Page 8: Neurotransmitters of Wakefulness

  • Arousal involves various neurons:

    • Norepinephrine (in locus coeruleus).

    • Serotonin (brainstem raphé nuclei).

    • Cholinergic neurons (basal forebrain and brainstem).

    • Histaminergic neurons (hypothalamus).

    • Orexin (hypothalamic neurons) aids sleep-wake transitions.

    • GABA (ventrolateral preoptic area) inhibits arousal.

Page 9: Brain Waves

  • Continuous electrical activity in the brain recorded as brain waves (EEG).

  • Wave character differs between wakefulness, sleep, and coma:

    • Classified into alpha, beta, theta, and delta waves.

Page 10: Alpha and Beta Waves

Alpha Waves

  • Frequencies: 8-13 Hz.

  • Parietal & occipital lobes.

  • Present during quiet, restful states in adults.

  • Elicits decreased attention levels; disappears in deep sleep.

Beta Waves

  • Frequencies: >14-80 Hz.

  • Parietal & frontal regions.

  • High-frequency, associated with alert wakefulness and specific brain activation.

Page 11: Theta and Delta Waves

Theta Waves

  • Frequencies: 4-7 Hz.

  • Parietal & temporal regions.

  • Found in children and during stress in adults; often seen in brain disorders.

Delta Waves

  • Frequencies: <3.5 Hz; high voltage.

  • Can occur in cortex.

  • Present in deep sleep and some organic brain diseases.

Page 12: Gamma Waves

  • Fast oscillations (38-80 Hz) during conscious perception and strong mental activities.

Page 13: What is Sleep?

  • A reversible state of unconsciousness; arousal possible by stimuli.

  • Active process with cyclic physiological phenomena.

  • Average sleep duration: 7.5 hours/day, approximately 114 days/year.

Page 14: Significance of Sleep

  • Functions include:

    • Neural maturation, learning, memory, metabolic energy conservation.

    • Restoration and repair of the body.

    • Support of the immune system, brain growth, particularly during REM sleep.

Page 15: Circadian Control of Sleep

  • Suprachiasmatic nucleus (SCN) regulates circadian rhythms.

  • Synchronizes with light-dark cycles and controls melatonin secretion (sleep hormone).

Page 16: Types of Sleep

  • Two main types alternate during the night:

    1. Slow-wave sleep (SWS, NREM): Deep restful sleep.

    2. Rapid eye movement sleep (REM): Active sleep.

Page 17: Stages of SWS

Stages 1 to 4

  • Stage 1:

    • Light sleep, transitional (1-7 min; 4-5% total).

    • EEG low-voltage, mix frequency, theta rhythm.

  • Stage 2:

    • Restful sleep (45-55% total).

    • EEG: appearance of sinusoidal waves called sleep spindles.

  • Stages 3 & 4:

    • Deep sleep (10-20% total; decreases with age).

    • EEG: delta wave, GH peak during this stage.

Page 18: EEG Changes

  • States characterized by different wave types.

    • Alert: Beta waves.

    • Quiet: Alpha waves.

    • SWS: Stages 1 to 4.

    • REM sleep: unique wave pattern.

Page 19: Characteristics of REM Sleep

  • Active sleep associated with dreaming.

  • Muscle tone depressed, but sporadic movements observed.

  • Irregular heart and respiratory rates.

  • Increased brain metabolism, with EEG patterns resembling wakefulness.

Page 20: Normal Sleep Cycle

  • Most of sleep is SWS with REM episodes about every 90 minutes.

  • Pattern: SWS followed by REM, repeated 4-5 times a night.

Page 21: Comparison of Sleep Type

EEG

Slow & high amplitude

Low voltage, rapid waves (similar to beta)

Motor Activity

Mild reduction

Marked depression of muscle tone

Heart Rate

Slightly reduced

Irregular

Dreaming

Rare

Common

Arousal

Easily awakened

Difficult to arouse

% of Sleeping Time

75%

25%

Page 22: Sleep Deprivation

  • Occurs when sleep needs are not met.

Effects of Sleep Deprivation

  • Neuro-behavioral deterioration:

    • Concentration and learning difficulties.

    • Slow reaction times and poor decision-making.

    • Decrease in short-term memory.

  • Physiological changes can occur, such as insulin resistance.

Page 23: Sleep Disorders

  • Types include:

    • Insomnia.

    • Fatal familial insomnia.

    • REM sleep behavior disorder (acting out dreams).

    • Bed-wetting (nocturnal enuresis).

    • Sleepwalking (somnambulism).

    • Night terrors.

    • Narcolepsy.

    • Obstructive sleep apnea (OSA).

Page 24: Insomnia and Fatal Familial Insomnia

  • Insomnia causes include stress, irregular schedules, and health issues.

  • Fatal familial insomnia: rare genetic disorder causing severe sleep impairments and dementia.

Page 25: REM Sleep Disorders

  • In REM sleep behavior disorder, individuals act out dreams due to a lack of normal paralysis during REM.

Page 26: Bed-Wetting

  • Also known as nocturnal enuresis, it is the involuntary passing of urine while asleep.

Page 27: Sleepwalking (Somnambulism)

  • More common in children; episodes can last several minutes.

  • Sleepwalkers do not recall their actions when awakened but they walk with eye open.

Page 28: Night Terrors

  • Associated with arousal from NREM and REM sleep; include sleepwalking and bed-wetting.

Page 29: Narcolepsy

  • Chronic disorder affecting sleep-wake regulation.

  • Characterized by cataplexy (sudden loss of muscle tone) and daytime sleepiness.

Page 30: Obstructive Sleep Apnea (OSA)

  • Common disorder leading to daytime sleepiness; breathing interruptions during sleep.

  • Typically begin to snore.

  • Affects approximately 24% of middle-aged men and 9% of women.